Loyalty is very important in every relation, be it husband and wife, family or others. One person who is not loyal to his/her beloved can`t be any marriage-material at all after my opinion. Loyalty is one of the foundations in a relationship. Like for instance if someone say something bad about your beloved, you back your beloved against that person. If you instead back up the “enemy”, how do you think your beloved would feel in such a circumstance. Not that loved, I would dare to say.
Or something like making fun of others. For one, I would like to say is that someone whom deliberately makes fun of others will have a lot of explaining to do to Allah on judgement day, for all the people he/she hurt. Another if someone makes fun of his/her loved ones in front of other, he/she is being rude and disrespectful and that should not be tolerated. For instance, We Muslims alhamdolillah love our Prophet (pbuh), so when someone makes fun of him making any cartoons just for fun, that is not ok with us. Most of us would want to protest against that and in some countries flags are burned, but mostly protests are held around the world. If you cannot be loyal you would have a difficulty being in relationship for a long time. So we should be careful how we interact with people. And we shouldn`t let our loved ones down. That can be terrible for the relation be it with anyone.
It could be that your loved ones are jealous of you, or that you have done something to hurt that person, so now he /she is taking back. In a civilized community I hope this wouldn`t happen, because they rather talk out their differences instead of any malicious act. Our Prophet (pbuh) would never ever approve of this and dislike it the most, as the character (subhanAllah) he has.